5G NR PRACH for NTN Use Case

Hi all,

I'd like to use NTN channel model for PRACH preamble detection using the example: https://de.mathworks.com/help/5g/ug/5g-nr-prach-detection-test.html. However, there are no NTN channels available. I tried to modify nrTDLChannel.m but it did not work. Please could you help me implement the NTN channel module or suggest ways to do it?

Thanks in advance!

Answer 1

[Alessandro Peloni]

Hi,

Since MATLAB R2024a, you can select NTN delay profiles within the nrTDLChannel system object by modifying the Delay Profile property: https://www.mathworks.com/help/5g/ref/nrtdlchannel-system-object.html#mw_fa3523ff-7296-4a0e-8334-03612f0863b9 .

I believe that this should satify your requirements. If this is not the case, I would suggest you contact MathWorks technical support specifying what is that you need and why the current offering is not enough for you.

I hope this helps.

Cheers,

Alessandro

[KK14]

Thanks Alessandro!

[KK14]

Hi,

is it possible to provide reference for the calculation of 'baseoffset' in the PRACH detection example? I am finding it hard to map it to the specifications from 3GPP and any help would be appreciated.

Thanks in advance!

[Alessandro Peloni]

Hi,

There is no official reference for the calculation of baseOffset. The reasoning behind that calculation is as follows:

1. Section 8.4.1.4.2 of TS 38.141-1 mentions that the base offset must be Ncs/2
2. The fraction of the Zadoff-Chu sequence occupied by Ncs/2 is: fZC = (Ncs/2)/LRA
3. For LRA=839, the Zadoff-Chu sequence spans a time in microseconds that can be computed as: tZC = 1e3/SubcarrierSpacing (where SubcarrierSpacing is defined in kHz)
4. Therefore, the length of Ncs/2 in microseconds is: baseOffset = fZC * tZC = (Ncs/2)/LRA * 1e3/SubcarrierSpacing

Hope this helps.

Cheers,

Alessandro

[KK14]

Thanks for the clear explanation, Alessandro!